This begs the question, given the USAF interest in SABRE, have REL decided in order increase their addressable market to develop a duel purpose engine design that both satisfies their design needs for SSTO but also allows for an easily achievable variant that satisfies USAF desire for hypersonic flight and when they talk about SABRE, is this the SABRE they're talking about?

No. REL were clear the cycle they described to the USAFRL was the same one given to the Von Karman Institute so the USAF could compare their results with a 3rd party. That's the SABRE 3.

SABRE IV's stated improvement is reduction in LH2 during airbreathing. REL were also clear if you want an air breathing engine their LAPCAT work is the way to go. USAFRL do not appear to have been interested in this work.

The idea that somehow hypersonic cruise is like arrested launch seems to come from the SCRamjet community.

The only part of an (RLV) launch that hypersonic cruise resembles is the re-entry.

The technical term for a rocket LV that is not accelerating during engine burn is crashing

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This begs the question, given the USAF interest in SABRE, have REL decided in order increase their addressable market to develop a duel purpose engine design that both satisfies their design needs for SSTO but also allows for an easily achievable variant that satisfies USAF desire for hypersonic flight and when they talk about SABRE, is this the SABRE they're talking about?

No. REL were clear the cycle they described to the USAFRL was the same one given to the Von Karman Institute so the USAF could compare their results with a 3rd party. That's the SABRE 3.

But the collaboration is ongoing, and ongoing REL is working on SABRE 4 so the USAF is interested in SABRE 4 and part of that is :

Quote

the proposed work will include investigation of vehicle concepts based on a SABRE derived propulsion system

Now couldn't that be describing a SABRE 4 derived engine such as I suggested might be possible based on the patents.

SABRE IV's stated improvement is reduction in LH2 during airbreathing. REL were also clear if you want an air breathing engine their LAPCAT work is the way to go. USAFRL do not appear to have been interested in this work.

The idea that somehow hypersonic cruise is like arrested launch seems to come from the SCRamjet community.

The only part of an (RLV) launch that hypersonic cruise resembles is the re-entry.

The technical term for a rocket LV that is not accelerating during engine burn is crashing

The difference between Scimitar and SABRE is that the former has a fan added for high efficiency subsonic cruise performance and :

Quote

The main difference between the Scimitar engine and the well investigated SABRE spaceplane engine is the design lifetime, 15,000hours compared to 50 hours. Apart from this, the Scimitar requirement is alleviated by reduced mass sensitivity relative to SABRE.

As has been discussed previously for a military engine for a highly specialized vehicle short lifetimes are more acceptable and the need for subsonic cruise on a hypersonic bomber is perhaps debatable. Other than that are you arguing Scimitar itself is a bad idea?

@lkmAFAIK REL had the SABRE 4 concept in mind long before the USAF collaboration. Like JS19 says, I think the USAF had access to the SABRE 3 cycle and not the SABRE 4 cycle, but I could be wrong about that.

@t43562The OneWeb consellation of satellites is planned to be operational by 2020, far too early for Skylon. That time-frame aside however, I still doubt Skylon would be a good fit for launching the proposed satellites. Each is reported to weigh only 125kg and work at an altitude of 1200km. Both weight and altitude don't match with skylon. Even with orbital boosters I think the satellites would be too small to form part of an economic cargo.

However, this is a good example of how a successful skylon programme doesn't negate the need for other types of operators. The saying 'horses for courses' will still be true in 2025.

@t43562... That time-frame aside however, I still doubt Skylon would be a good fit for launching the proposed satellites. Each is reported to weigh only 125kg and work at an altitude of 1200km. Both weight and altitude don't match with skylon. Even with orbital boosters I think the satellites would be too small to form part of an economic cargo.

I presume they have been designed to fit the launchers available to them. Perhaps they would not look the same if Skylon was on the scene.

Yes, no doubt designed partially with existing launch capability in mind (and partially with the need to fulfil job specifications).

But agreed of course, increased launch capability as provided by skylon (if successful) will open up a whole new ball-game in space access and will change how people view space in terms of reliability of launch, flexibility of launch, vastly reduced lead-in times (on the order of days if needed) and perhaps other stuff that we haven't considered yet.

@t43562The OneWeb consellation of satellites is planned to be operational by 2020, far too early for Skylon. That time-frame aside however, I still doubt Skylon would be a good fit for launching the proposed satellites. Each is reported to weigh only 125kg and work at an altitude of 1200km. Both weight and altitude don't match with skylon. Even with orbital boosters I think the satellites would be too small to form part of an economic cargo.

The trip to GEO is planned to use the Skylon Upper Stage. That's designed to carry about a 6500Kg payload to GTO.

1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.

But now the timetable does not look feasible for Skylon to be used.

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JS19**1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.**

Yes, but each has to be inserted into a different position and thus each would require their own booster. If you look at the manual for skylon there appears to be room for just one booster load, and that load would be of considerably great weight than each of these satellites. Not that skylon couldn't launch them, just that they wouldn't be the target market.

JS19**1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.**

Yes, but each has to be inserted into a different position and thus each would require their own booster. If you look at the manual for skylon there appears to be room for just one booster load, and that load would be of considerably great weight than each of these satellites. Not that skylon couldn't launch them, just that they wouldn't be the target market.

Being a layman is fun - I can suggest all sorts of impossible things and claim I don't know any better :-). Imagine that you had a SUS-like booster which carried multiple satellites. Could it, perhaps, boost itself to a slightly lower orbit than 1200km and let a small electric thruster on each satellite itself finish the job? I'm a bit unclear about whether 2 objects in the same shaped orbit but with a slight altitude difference would move relative to one another - playing Kerbal Space program leads me to think they do move. If that's right then the dispenser in it's lower orbit would be able to release satellites at intervals which would boost themselves into the 1200km orbit. It might be at 1199km so the boost would only be the extra speed needed to in increase the radius by 1km. Such a small difference might mean it took months to deploy but the dispenser could perhaps fill a band for the cost of 1 Skylon launch.

Being a layman is fun - I can suggest all sorts of impossible things and claim I don't know any better :-). Imagine that you had a SUS-like booster which carried multiple satellites. Could it, perhaps, boost itself to a slightly lower orbit than 1200km and let a small electric thruster on each satellite itself finish the job? I'm a bit unclear about whether 2 objects in the same shaped orbit but with a slight altitude difference would move relative to one another - playing Kerbal Space program leads me to think they do move. If that's right then the dispenser in it's lower orbit would be able to release satellites at intervals which would boost themselves into the 1200km orbit. It might be at 1199km so the boost would only be the extra speed needed to in increase the radius by 1km. Such a small difference might mean it took months to deploy but the dispenser could perhaps fill a band for the cost of 1 Skylon launch.

You might like to look at the 1st generation Orbcomm satellites.

Most were deployed by single Pegasus XL launches to populate a ring of 8 satellites, each being designed like a pizza so they could be stacked together.

While the bus could supply some separation IIRC most was done by the satellites small thrusters or simple gravitational drift.

Orbcomm was one of 3 early 90's constellations (Globalstar and Iridium being the others) that actually got built. IIRC it offered the least bandwidth but was the only one that made (or came close to making) a profit. Something this new generation of constellation promoters (and their investors) might like to keep in mind.

The first reduces air drag (which is actually the largest residual force on satellites below 1000Km) but raises the radiation exposure levels, so either the electronics cook faster or you have to spend mass on shielding, making them less capable, or you replace more frequently. How much more frequently would be a key design decision to trade replacement versus making them tough enough to survive as long as less exposed satellites.

« Last Edit: 06/29/2015 12:11 PM by john smith 19 »

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JS19**1200Km is about 1/35 of GEO. That suggests an SUS could carry a pretty big number of them. With no changes that would 48 sats. I'd guess at 1/35 the altitude you could increase the quite a bit.**

Yes, but each has to be inserted into a different position and thus each would require their own booster. If you look at the manual for skylon there appears to be room for just one booster load, and that load would be of considerably great weight than each of these satellites. Not that skylon couldn't launch them, just that they wouldn't be the target market.

Being a layman is fun - I can suggest all sorts of impossible things and claim I don't know any better :-). Imagine that you had a SUS-like booster which carried multiple satellites. Could it, perhaps, boost itself to a slightly lower orbit than 1200km and let a small electric thruster on each satellite itself finish the job? I'm a bit unclear about whether 2 objects in the same shaped orbit but with a slight altitude difference would move relative to one another - playing Kerbal Space program leads me to think they do move. If that's right then the dispenser in it's lower orbit would be able to release satellites at intervals which would boost themselves into the 1200km orbit. It might be at 1199km so the boost would only be the extra speed needed to in increase the radius by 1km. Such a small difference might mean it took months to deploy but the dispenser could perhaps fill a band for the cost of 1 Skylon launch.

Dwell time for an upper stage maneuver bus might be the issue here. If you are targeting 6-10 sats per orbital plane, the basic options are one bus per plane or one bus for the whole operation, but a single bus means a much longer duration of operations (which implies electric with a substantial solar array). Going to a slightly lower orbit and using precession to swap planes might be viable, assuming final orbit raising via electric thrusters on the sats is reasonable, as a means to reduce dwell time.

Dwell time for an upper stage maneuver bus might be the issue here. If you are targeting 6-10 sats per orbital plane, the basic options are one bus per plane or one bus for the whole operation, but a single bus means a much longer duration of operations (which implies electric with a substantial solar array). Going to a slightly lower orbit and using precession to swap planes might be viable, assuming final orbit raising via electric thrusters on the sats is reasonable, as a means to reduce dwell time.

Except the bus in this case would be the SUS, which is currently spec'd at having a 10 use life time and would be recovered by the Skylon for return to Earth and refueling.

A completely reusable system changes deployment options quite a lot, especially given the target payload (125Kg?) for a single unit is much smaller than the target for a much bigger single payload to a much higher orbit.

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Dwell time for an upper stage maneuver bus might be the issue here. If you are targeting 6-10 sats per orbital plane, the basic options are one bus per plane or one bus for the whole operation, but a single bus means a much longer duration of operations (which implies electric with a substantial solar array). Going to a slightly lower orbit and using precession to swap planes might be viable, assuming final orbit raising via electric thrusters on the sats is reasonable, as a means to reduce dwell time.

Except the bus in this case would be the SUS, which is currently spec'd at having a 10 use life time and would be recovered by the Skylon for return to Earth and refueling.

A completely reusable system changes deployment options quite a lot, especially given the target payload (125Kg?) for a single unit is much smaller than the target for a much bigger single payload to a much higher orbit.

Which implies cluster deployers (AKA corncob upper stages) will not be based on the currently envisioned cryogenic fueled SUS, but more like a SUS-like electric tug. So cSUS and eSUS variants?

Which implies cluster deployers (AKA corncob upper stages) will not be based on the currently envisioned cryogenic fueled SUS, but more like a SUS-like electric tug. So cSUS and eSUS variants?

I don't think so. The dispenser is part of the payload. It's designed to fit on the front of the upper stage.

In Skylon's case the US sits in the payload but it's still the upper stage.

I don't see anyone who they are booked with announcing an ion drive upper stage. That's more of a "space tug" concept.

I would expect they will deploy like most of these constellation concepts. Upper stage burns AFAP, gravity drift if needed and satellite thrusters if absolutely necessary.

BTW IIRC the latest Skylon User Manual has a description of deploying an ion drive comm sat. In it the SUS deploys it about 5000 Km (above the radiation belt) and avoids the "radiation crockpot" effect.

No I don't think a specific ion drive US will be necessary.

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An article in Aviation Week Titled "Reaction Engines Reveals Secret Of Sabre Frost Control Technology" stated that Richard Varvill spoke at the American Institute of Aeronautics and Astronautics International Space Planes and Hypersonics conference and explained how the frost control system works.

Mark Thomas also explained why they finally patented the frost control mechanism. He said ďThe trigger for patenting was the awareness that to execute this program we are going to have to involve other companies. You canít keep trade secrets very long in that situation, so it is better to be protected formally and legally on the clever stuff.Ē

At the end of the article it states that:

The company is developing the Sabre engine principally for the Skylon single-stage-to-orbit spaceplane. But the propulsion system and its pre-cooler technology are attracting wider interest for potential aircraft and two-stage launch vehicle applications

**The trigger for patenting was the awareness that to execute this program we are going to have to involve other companies. You canít keep trade secrets very long in that situation, so it is better to be protected formally and legally on the clever stuff**

That was going to be the only reasonable outcome. Other companies they're hoping to work with obviously didn't want the risk of doing business with REL unless there was legal protection on the core technology. Now the question is which companies are REL in negotiation with?